A new study based on neurological data and brain specimens from a group of nuns, known as the Nun Study, confirms that language skills earlier in life are linked to Alzheimer's disease risk in older age. But it also adds new, puzzling information to our knowledge about the disease: The brains of the women who did not have Alzheimer's symptoms had larger brain cells, or neurons, but not necessarily fewer of the plaques and tangles characteristic of the disease. To assess language skills early in life, researchers examined essays written by 14 women when they entered the convent, looking for the number of ideas expressed in every group of 10 words. A previous study linked grammatically complex writing skills to a decreased risk of dementia, and this study confirmed it: The essays written by women who maintained their memory scored 20 percent higher on language tests. "This is the second independent sample with the same result. We're back to the metaphor of the brain as a computer and a muscle," said [geriatric psychiatrist] Dr. Gary J. Kennedy.... "In volunteers who had no signs of Alzheimer's but did have the plaques and tangles, the neurons were actually larger and more functional with more connections" [
For the study, published in the journal Neurology, the researchers also went one step further by examining brains donated by 38 nuns when they died. Researchers found that the brains of some of the nuns who did not suffer memory loss had the trademark tangles and plaques found in Alzheimer's patients. Says study author Juan Troncoso:
"A puzzling feature of Alzheimer's disease is how it affects people differently.... One person who has severe plaques and tangles, the telling signs of Alzheimer's disease in their brains, may show no symptoms affecting their memory. Another person with those same types of plaques and tangles in the same areas of the brain might end up with a full-blown case of Alzheimer's disease" [CBC News].
The scientists found that the nuns who did not suffer from memory loss had the largest neurons. The findings
suggested that a growth in brain cells might be part of the body's early response to the onset of dementia, and this might help to prevent memory impairment. Troncoso said: "Perhaps mental abilities at age 20 are indicative of a brain that will be better able to cope with diseases later in life" [BBC News]. Although the study evaluated a small, select group of subjects, researchers hope to explore further whether language skills can predict Alzheimer's risk later in life.
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Image: flickr / PinkMoose